Question

What is the chemical formula of rust?

Answer 1

Rust:

1. The slow reaction of iron in the presence of water and Oxygen or both through the transfer of electrons from Iron to Oxygen.
2. The chemical formula of rust is ${\mathrm{Fe}}_2{\mathrm{O}}_3$.

The chemical reaction of the rusting process:

1. Oxygen reduction ${\mathrm{O}}_2\left(\mathrm{g}\right)+4{\mathrm{e}}^{-}+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 4{\mathrm{OH}}^{-}$
2. Iron oxidation: $\mathrm{Fe}\left(\mathrm{s}\right)\to {\mathrm{Fe}}_2\left(\mathrm{s}\right)+2{\mathrm{e}}^{-}$
3. Redox reaction: $3{\mathrm{Fe}}_2\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to {2\mathrm{Fe}}_3\left(\mathrm{s}\right)+{\mathrm{O}}_2^{-}\left(\mathrm{g}\right)$
4. Acid-base reaction: $$\begin{gathered} {\mathrm{Fe}}_2\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\rightleftharpoons \mathrm{Fe}{\left(\mathrm{OH}\right)}_2\left(\mathrm{s}\right)+2{\mathrm{H}}^{+} \\ {\mathrm{Fe}}_3\left(\mathrm{s}\right)+3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\rightleftharpoons \mathrm{Fe}{\left(\mathrm{OH}\right)}_3\left(\mathrm{s}\right)+3{\mathrm{H}}^{+} \end{gathered}$$
5. Dehydration process: $$\begin{gathered} \mathrm{Fe}{\left(\mathrm{OH}\right)}_2\left(\mathrm{s}\right)\rightleftharpoons \mathrm{FeO}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Fe}{\left(\mathrm{OH}\right)}_3\left(\mathrm{s}\right)\rightleftharpoons \mathrm{FeO}\left(\mathrm{OH}\right)\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ 2\mathrm{FeO}\left(\mathrm{OH}\right)\left(\mathrm{s}\right)\rightleftharpoons {\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \end{gathered}$$